Well casing milling device



Sept. 28, 1954 E. J. ROBISHAW WELL CASING MILLING DEVICE 2 Sheets-Sheet 1 Filed April 22, 1950 INVENTOR. Earl .I llobiahau/ BY M 61 ATTORNEY P 1954 E. J. ROBISHAW WELL CASING MILLING DEVICE 2 Sheets-Sheet 2 Filed April 22, 1950 all 44% w mg h 2 ll l l ll. Ill. .||..|||I

- JNVENT R. Earl l Rlrbbluw Maw ATTORNEY Patented Sept. 28, 1954 WELL CASING MILLING DEVICE Earl J. Robishaw, Houston, Tex.

Application April 22, 1950, Serial No. 157,533

9 Claims. 1

This invention relates to a well casing milling device, and more particularly to an improved milling tool adapted for use in cutting and removing pipe from the bore of a well.

In the production and operation of wells, and particularly oil wells, it is frequently necessary to remove a portion of the casing in the well at some predetermined location for side tracking operations, or to expose a producing stratum, or for other purposes. Thus, it may be desirableto remove a section of the casing to allow a whipstock to be set in an open window, or the casing may be cut away to expose a sand stratum or other potentially productive formation which has been previously cased ofi.

Such operation must frequently be conducted at great depths in the Well which presents serious problems in the character of the tools employed as well as in the manner in which the operation is carried out, because of the great weight of the operating string by which such tools are operated and frequent deviation of the bore of the well from the vertical.

Some of the serious problems above mentioned are caused by the inability of the milling tool to quickly and efficiently mill away the casing to provide the window therein for the purpose above mentioned. The tools now in use perform such milling operation by rotation of the cutters provided on the tool by rotation of the string to which the tool is attached. This straight rotation causes the cutters to groove and this grooving stops the milling or cutting of the casing, and damages the cutters. Therefore, it is very important to prevent such grooving and, in lieu thereof, to cause them to wear straight across the casing being milled.

It is an object of the present invention, therefore, to provide a milling tool for severing and milling a well casing, which tool has cutters that are adapted to be extended across the severed end of the casing and also to embody means for engagement with the casing to cause such cutters to move laterally back and forth across the end of the casing as the tool is rotated thereon. By

the employment of such means the life of the cutters is greatly increased and more casing can be out or milled in a shorter period of time and, in addition thereto, such means makes possible the cutting of pipe that otherwise could not be cut by tools now in use. Thus, this invention now makes it possible-to have windows milled in well casings where otherwise it would have been uneconomical to have attempted to do so.

A more specific object of this invention is to provide removable eccentric means rotatably mounted or attached to a milling tool to maintain the tool off center or eccentric of the well bore so that upon rotation of the tool it will rotate close to one side of the wall casing to be severed and away from the opposite wall whereby a simultaneous lateral and rotation action will be imparted to the knives or blades on the milling tool.

The above and other objects and advantages of the invention will appear from thefollowing detailed description of a preferred embodiment of the same, when considered in conjunction with the drawings annexed, wherein Figure 1 is a vertical, central, cross-sectional view of the invention with the knives in retracted position;

Figure 2 is a side elevational View of the invention operatively positioned in a well casing;

Figure 3 is a vertical, central, cross-sectional view of the invention operatively positioned in the casing with the knives in extended cutting pos' tion; 1. Figure 4 is a cross-sectional view taken along the line i-d of Figure 3, looking in the direction indicated by the arrows; and

Figure 5 is a cross-sectional View taken along the line 55 of Figure 3, looking in the direction indicated by the arrows.

Referring to the drawings in greater detail, the numeral 1 indicates a tubular cutter body or mill body having an internally threaded upper end for attachment to the lower end of an operating string indicated at 2. The body I has an internal bore 3 forming an internal shoulder t near its lower end, and a tubular stem 5, having an enlarged portion i3 forming an external shoulder i, fits in the body and is supported therein on the shoulder with the lower end of the stem extending below the body. The lower end of the stem 5 is externally threaded as at 9 to receive the internally threaded conical guide nut it! provided to hold the eccentric guide assembly in position, as hereinafter described.

An eccentric guide assembly, having a tubular body 52, formed internally to fit over the reduced end portion of body I and about the lower end of the stem 5, is provided to cause the blades, hereinafter described, to move laterally at the same time they are being rotated and, thus, to produce a simultaneous cutting and sawing action which materially increases the milling speed of the tool, and also enables it to cut pipe that otherwise could not, due to its hardness, be severed by the standard milling tool now in use,

The tubular body it, as stated above, is held in place on the lower end of the milling tool by the conical guide nut it. The internal facing shoulders of the lower end of the body 3 and the upper end of the conical nut are provided, respectively, with the anti-friction bearings Hi and it.

3 Packing or seal rings l8 and I! are provided between the body I and the guide body 12 and between the guide nut l and said guide body, respectively, to prevent entrance of foreign matter into the bearings l4 and I5.

The outwardly extending, spaced, members, or ribs is are provided on the periphery of the body 12 for engagement with the inside of the Well casing as that shown at 2B. These ribs or radially extending members may be formed integrally with the body or shaped in any preferred manner to accomplish the desired purpose. As shown in Figure 5, these ribs [9 are progressively widened, or extended outwardly, radially of the body I2, thereby providing an outside diameter for the assembly that is off center or eccentric with the axial bore of the body I2 through which the stem is extended.

The cutter body 1 has an outwardly thickened portion 22 located approximately centrally of the body, and a reduced lower end portion, the portion 22 being provided with side slots 23, whose upper margins extend out at substantially right angles to the axis of the body forming shoulders 2 Pivotallymounted in the slots 23 are the cutter blades 25, pivoted on pivot pins 21, each of which has a head 29 at one end and a hole 3!! at the other end for the reception of a cotter pin or other securing means.

The slots 23 are suihciently long to permit the blades 26 to be retracted into them in inactive position, as seen in Figure l. The blades are extended inwardly beyond their pivots and the inner ends are reduced in width in order to provide clearance sufiicient to permit the outer cutting portions of the blades to be retracted into the slots when in inactive position, as shown in Figure l.

A bushing 32 is disposed in the body I in engagement with a shoulder 33 therein, and a cylinder 34 is carried on the upper end of the bushing by an enlarged portion 35, so that the cylinder is spaced somewhat from the bushing to provide an annular passage 36. Openings 3'! are provided in the cylinder communicating with the passage 30 and the interior of the cylinder. The cylinder is spaced at its lower end from the inside of the body to form a continuation of the passage, as will be seen in Figures 1 and 3. Packing material Bil may also be provided on the cylinder 34 so that the cylinder is retained securely in place when the body is attached to the string 2. The cylinder 34 is also provided with a beveled seat 40 at its lower end.

Mounted in the cylinder 34 is a piston 4 I carrying a piston ring 42 held on the upper end of the piston by a washer 43 and nut 44 secured to the threaded extension 45. The piston has a passage 46 opening into the interior of the cylinder above the piston, and leading into side passages 48, which open laterally into the cylinder below the piston ring 42, as seen in Figures 1 and 3.

The piston has a tapering shoulder 50 which fits against the beveled seat 49 when the piston is in its upper position.

An annular recess 52 is provided in the piston for the reception of the inward ends of the cutter blades 26 to operate the knives when the piston moves up or down, and the lower end of the piston forms a seat for a spring 54 which bears on an internal shoulder 55 in the stem 5 to urge the piston upwardly in the cylinder.

Vertical grooves 56 are formed about the periphery of the enlarged portion 6 of the stem 5,

as seen in Figure 4, to permit the passage of fluid between the body and the stem and these grooves communicate with the interior of the tubular stem by passages 57 as indicated in dotted lines in Figure 1.

From an examination of the drawings it will be seen that in the condition of the device shown in Figure 1, fluid from the string may pass through the passages 46 and lit, into passage 36 and downwardly through grooves 5t and passages 51 into the passage 60 of the stem and thence into the casing below the tool. In this condition of the tool the piston 4| is in its upper position, and the bottom of the cylinder is closed by the tapered shoulder 50 so that fiow of fluid is restricted and the piston may be forced downwardly by an increase of pressure in the string.

When the piston is moved downwardly, by the pressure of fluid in the string, overcoming the force of the spring 54 to occupy the position seen in Figure 3, fluid from the string may fiow through holes 31 and take the course previously described, and fluid also flows through passages 456, it and out of the bottom of the cylinder t l, so that the flow will be greater in the condition of the device shown in Figure 3, than in that shown in Figure 1.

In using the milling device, the same is attached to an operating string and lowered into the well, in the condition seen in Figure 1, wherein the knives 26 are retracted and the piston t! is in its upper position. When the tool has reached the desired location opposite the portion of the casing 20 to be milled, the fluid pressure in the string can be suitably increased, moving piston M downwardly and forcing the knives into cutting engagement with the casing. Rotation of the string then results in cutting through the casing at the selected location. After the casing has been severed, the knives 26 will be extended through the opening formed and brought into cutting relation with the severed end of the casing. 'The knives then bear against the shoulders 24 at the upper extremities of the slots 23, and. the pressure exerted by the blades in milling the casing may be regulated by controlling the weight applied thereon through the operating string. Subsequent rotation of the string will then cause the knives to mill away the casing to the extent desired.

It is to be noted that the engagement of the spaced members or ribs it with the casing below the blades 26 maintains the vertical axis of the tool oil center with relation to the vertical axis of the casing or bore of the well. Upon rotation of the string the body E2 of the eccentric guide assembly remains substantially stationary the extended ribs l9 contacting one side of the Wall of the casing. However, the body l is permitted to rotate relative to the body i2 by the bearings [4 being located between such bodies. Thus, the body I of the tool rotates close to one side of the wall casing and away from the opposite wall to produce the simultaneous cutting action of the blades as hereinabove explained.

As previously explained, when the device is in the condition shown in Figure l, and during the operation of severing the casing, fluid may pass down through the tool and on down into the casing, whence it flows upwardly about the eccentric guide l2 and passes up out of the well carrying with it any cuttings or other material.

In the condition of the device seen in Figure 3, however, with the knives fully extended, and the piston in its down position, a full circulation of fluid through the tool takes place, thus providing for the disposal of the relatively greater quantity of cuttings formed during the milling operation.

Upon completion of the milling the tool can be removed from the well by withdrawing the operating string, and the blades will be retracted for this purpose by operation of the spring 54 urging the piston 4| upwardly to the position illustrated in Figure 1. Should the blades fail to retract they will be pressed inwardly to retracted position by engagement with the casing above the milled-out portion as the tool moves upwardly out of the well.

By suitably regulating the pressure exerted on the cutters, by controlling the weight applied by the operating string, the speed of the milling operation can be adjusted to satisfy particular operating conditions, such as the hardness of the material of the casing.

What I claim is:

l. A milling tool for use in performing a cutting operation on a pipe in a well, said tool comprising, a body adapted to be connected to an operating string and rotatable with said string, a cutter blade mounted on the body for radial movement relative thereto into a position to operate on a pipe in a well to sever the pipe and mill away a section thereof, and eccentric means carried by said body for relative rotation about the axis of rotation of said body and engageable with the pipe for maintaining the axis of rotation of. said body eccentrically of the pipe and substantially fixed.

2. A milling tool comprising, a :body adapted to be connected to an operating String for rotation thereby, cutter blade means movably mounted on the body and rotatable therewith, said blade means being movable radially on said body to a position in engagement with a pipe in a well, and means including eccentric means carried by said body for relative rotation about the axis of rotation of said body and engageable with the pipe for causing relative radial movement between said blade means and the pipe during rotation of said body.

3. A milling tool comp-rising, radial cutter blade means operatively secured to an operating string and rotatable with said string, said cutter means being mounted on said string for movement relative thereto into a position to operate on a pipe in a well to sever the pipe and mill away a section thereof, and means supported on said string for relative rotation about the axis of rotation of said string and engageable with the pipe for causing relative radial movement between said cutter means and the pipe as said string is rotated.

-4. A milling tool comprising, a body adapted to be connected to a tubular operating string and rotatable with said string, a cutter blade mounted on said body for movement relative thereto into cutting position to operate on a pipe in a well to sever the pipe and mill away a section thereof, means in said body operatively engaging said cutter blade and operable by the pressure of an operating fluid in said string to move said blade into cutting position, and means mounted on said body for relative rotation about the axis of rotation of the latter and coopera'ble with the pipe for causing relative lateral movement between said cutter and the pipe as said body is rotated.

5. In a casing milling tool for use in cased bore holes, a body adapted to be connected to an operating string and rotatable by said string, a cutter blade mounted on the body for movement relative thereto into position to seat on an end of, and cut away a portion of, the casing in the hole, and means carried by said body for relative rotation about the axis of rotation of the latter and engageable with the casing to maintain the body in a relatively fixed ofi' center position with respect to the casing.

6. A casing cutting and milling tool for use in cased bore holes comprising, a body adapted for connection to an operating string, a cutter blade mounted on the body, said blade being movable radially relative to the body to a, position whereby it is in cutting engagement with the well casing, and means rotatably carried by said body to hold the axis of rotation of the latter off center in said casing and substantially fixed therein in order to force said blade to move relatively radially of said casing as said body is rotated.

7. A milling tool for severing the casing of a cased bore hole and milling away a section thereof, said tool comprising a body adapted to be connected to an operating string and rotatable therewith, at least one cutter mounted on said body for outward radial movement into cutting engagement with the casing, and eccentric guide means mounted on said body for relative rotation about the axis of rotation of the latter and engageable with the casing for effecting rotation of said body about a substantially fixed axis eccentric with respect to the axis of the casing.

8. The structure defined in claim 7 in which the guide means is detachably mounted on the body for replacement with guide means of different size in order to accommodate the tool to casings of different inside diameter.

9. An eccentric assembly for use with a milling tool that is adapted to be lowered into a cased well and rotated therein for severing and milling away a sec-tion of the casing thereof, said assembly comprising: an elongated circular body having an axial bore adapted to be journalled on the milling tool for unlimited relative rotation therebetween about the rotational axis of the tool; and a plurality of longitudinally-extending circumferen'tially-spaced radial vanes fixed on said body and having outer faces of considerable area lying in a circle eccentric with said bore'and of a diameter only slightly less than that of the casing to be milled, said vanes having considerable circumferential spacing to provide passageways therebe'tween for flow of milling fluid between said body and the casing, the outer faces of said vanes being adapted to engage a portion of the wall of the casing to restrain said assembly against rotation and thereby maintain the rotational axis of the tool substantially fixed and eccentric with respect to the casing axis.

References Cited in the file of this patent UNITED STATES PATENTS 

